\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{circuitikz}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes}
\ctikzset{bipoles/length=1cm}
\begin{document}
\small
\begin{circuitikz}[>=latex, scale=1,european]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
\draw (0,1.3)--(0,0)--(.9,0);
\draw (.9,3) to [american inductor] (.9,0);
\draw (.9,3)--(0,3)--(0,1.7) ;
\draw (1.50,0) to  [american inductor,name=xq] (1.5,3);
\draw (xq.center) --(5.8,1.5) to [R=$R$,name=dz] (5.8,3)--(1.5,3);
\node at (xq.left)[below right]{$b$};
\node at (xq.right)[above right]{$a$};
\node at (xq.center)[above right]{$O$};
\node at (dz.left)[right=1mm]{$-$};
\node at (dz.right)[right=1mm]{$+$};
\ctikzset{diodes/scale=0.6}
\draw (1.5,3) to[full diode=$D_1$](4,3);
\draw (1.5,0) to[full diode=$D_2$](4,0)--(4,3);
\draw (0,1.3) [fill=white]circle (1.5pt);
\fill (4,3) circle (1.5pt);
\draw (0,1.7) [fill=white]circle (1.5pt);
\node at (0,1.5){$\sim$};
\draw [ultra thick](1.2,1)--(1.2,2);
\node at (1.2,2.5){$B$};
\draw [<->](2.2,0)--(2.2,1.5)node [midway,right]{$u$};
\draw [<->](2.2,3)--(2.2,1.5)node [midway,right]{$u$};
\draw [->](3.8,2.8)--++(1.4,0)--++(0,-1.15)--++(-0.8,0);
\draw [densely dashed,->](3.8,0.2)--++(0.4,0)--++(0,2.4)--++(0.8,0)--++(0,-0.75)--++(-0.6,0);
%\draw [ultra thick] (3.75,3.25)--(3.75,2.75);
% \node at (5.25, .8){$-$}; \node at (5.25, 2.2){$+$};
\end{circuitikz}
\end{document}